Water-operated wash brushes are known for use in many cleaning applications, such as cleaning floors, walls, mechanical work pieces, and vehicles. Such wash brushes commonly include an upper casing into which a nozzle forcefully directs a tangential jet of water that rotatably drives a turbine-like impellor, which in turn through appropriate reducing gears, drives a wash brush supported in depending relation to the casing at a rotary speed less than the turbine. The wash brush is constantly wetted by the water that produces the brush rotation.
In order to protect the reducing gears from the water stream so as not to impede rotary operation of the brush, it is known to form the impellor with an upwardly opening recess, which together with the top of the casing, defines a protective chamber. A disadvantage of such design is that all of the gearing must be supported by the top of the casing, which can cause assembly difficulties. With the gearing contained within the chamber between the impellor and the top of the casing, they also are not easily accessible. Moreover, it is common to form the casing of inexpensive clear plastic material, which enables the user to observe the operation of the impellor. In such case, with the reducing gears disposed over the turbine, they are directly viewable through the top of the transparent casing, which can detract from the ascetic appearance. Moreover, if the brush is briefly turned in an upside-down direction during a washing operation, water can quickly accumulate in the casing which can impede operation of the brush. While proposals have been made for supporting the reducing gearing on the underside of the impellor, such designs are disadvantageous in that the gears can be exposed to the tangentially directed water stream, which can impede their operation. The gearing further is exposed to water which backsplashes from the rotating brush.